All patients with H1N1 pandemic influenza admitted to the ICU of the University Medical Center Utrecht were eligible for inclusion. Patients received oseltamivir at a dose determined by their treating physician, and blood samples were drawn at t = 0, 1, 2, 3, 4 and 8 h on day three of treatment. Oseltamivir and oseltamivir carboxylate plasma concentrations were determined by HPLC–MS/MS [3]. The area under the concentration–time curve from 0 to ...